The objectives of this study are to investigate the synthesis of the different types of collagen, including types I, III and IV, by cultured vascular smooth muscle cells derived from normal arteries, normal veins, and intimal atherosclerotic plaques, and to examine the role of serum lipoproteins (VLDL, LDL, HDL) and delipidated serum on stimulating or modifying the production and deposition of these connective tissue proteins. The experimental protocol includes establishing homogeneous cultures of these cells in vitro, exposing them to tritiated proline and glycine, and then isolating and characterizing the labeled collagens synthesized by these cells using differential salt precipitation, gel electrophoresis, ion exchange and molecular sieve chromatrography. After having established the relative amount and types of collagen synthesized by these cells and the effect that serum lipids may exert on their production, studies will be undertaken to measure the activity of several important post-translational modifying enzymes of collagen alpha chains, including prolyl hydroxylase, procollagen peptidase, and lysyl oxidase which are involved in the hydroxylation, the cleavage of the precursor, procollagen and the cross-linking of collagen, respectively. The final objective is to establish the endothelial cell as a source of basement membrane associated collagen in arteries and veins by studying its synthesis in cloned homogeneous cultures of endothelial cells in vitro.